1. Field of the Invention
The present invention relates to a method and apparatus for producing powdered metal compacts. More particularly, the present invention relates to a method and apparatus for producing hard metal wire drawing dies, particularly compacts or wire drawing dies with fine holes.
2. Description of the Prior Art
In normal practice, metal compacts are produced by compacting powder metals such as tungsten carbide-cobalt mixtures in a press. Generally, two opposing punches are used to compact the powder metal mixture under pressure. Typically, the punches are designed such that they impart a unique geometry to the compacted powder metal. The compacted metal is then sintered to form the "hard metal" product.
One use for the metal compacts is as wire-drawing dies. Wires having diameters as fine as 0.004 or 0.005 inches can be formed using such a die. These dies are pressed by a punch which generates the very fine hole in the compact by use of a thin, elongated stem. In holes larger than 0.015 inches, the opposing punch is provided with a reciprocating hole. For fine holes (less than 0.015 inches), the opposing punch may be provided with a depression opposite the stem of the first punch. This leaves a bubble of compacted metal which covers the hole formed by the stem. By using such a method, the precision placement of the opposing punches is not as critical as when the stem must enter a reciprocating hole in the opposing punch, thereby reducing the risk of breakage of the fine stem of the first punch.
By providing this depression in the opposing punch, a secondary operation is needed to form the wire-drawing die. The bubble left by the depression must be ground off to expose the hole formed by the stem. In addition, some dies require a back tapered hole to relieve the stresses on the wire during the drawing operation. Such a back-taper requires an additional secondary operation to create the desired hole contour. Accordingly, there is a need for a one-step method for producing a compaction of powdered metal components having very small holes and an apparatus for accomplishing the same.